镜面粗糙度对远紫外望远镜能量集中度的影响

Effects of mirror surface roughness on encircled energy for far ultraviolet telescopes

  • 摘要: 远紫外空间成像设备镜面粗糙度严重影响成像质量,成像质量可用能量集中度来表征。拟用余弦相位调制光栅分析方法定性说明镜面粗糙度RMS对能量集中度的影响;通过傅里叶光学线性系统理论建立了普遍的面传递函数,得到了角度能量和能量集中度的分布情况,并以设计上达到衍射极限的1 216 (1=0.1 nm)远紫外望远镜为对象,在镜面粗糙度RMS值远小于波长的假定情况下,得到了能量集中度与主次镜面粗糙度RMS和面自相关长度的关系,并预测了镜面粗糙度引起的分辨率误差在0.171 5时对镜面加工的要求,即主次镜镜面RMS小于31 ,面自相关宽度大于1波长,这对于实际的加工具有指导意义。

     

    Abstract: The image quality was degraded by the surface roughness of astronomy imaging applications, and it might be specified in terms of fractional encircled energy. Relationship between the encircled energy and roughness RMS was qualitatively analysed by cosine phase grating model,moreover,the effective transfer function of the surface was built drew on Fourier optical linear systems theory, then the associated angle spread function as well as encircled energy were deduced. For 1 216(1=0.1 nm) far ultraviolet telescope which closed to diffraction limit and in the terms of primary and secondary mirrors roughness RMS were far less than one wavelength, encircled energy versus RMS roughness and autocovariance width could be infered. So resolution error caused by surface roughness was limited in 0.171 5, the manufacturing requirement for mirrors roughness RMS was less than 31 and autocovariance width was longer than one wavelength. It's useful for our manufacturing guiding significance.

     

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